Three down, Sixty three to go: ALMA reaches key milestone

After more than ten years of design and construction by scientists and engineers across the globe, the Atacama Large Millimeter/submillimeter Array (ALMA) has passed a key milestone crucial for the high quality images that will be the trademark of this revolutionary new tool for astronomy. Astronomers and engineers, have, for the first time, successfully linked three of the observatory's antennas at the 5000-metre elevation observing site in northern Chile. Having three antennas observing in unison paves the way for precise images of the cool Universe at unprecedented angular resolution. Several groups in the UK have played a leading role since its inception, making important contributions to the design and construction of ALMA’s receiver systems, cryogenics, and software.

On 20 November 2009 the third antenna for the ALMA observatory was successfully installed at the Array Operations Site, the observatory’s “high site” on the Chajnantor plateau, at an altitude of 5000 metres in the Chilean Andes.

Later, after a series of technical tests, astronomers and engineers observed the first signals from an astronomical source making use of all three 12-metre diameter antennas linked together, and are now working around the clock to establish the stability and readiness of the system.

The UK’s involvement includes the Science and technology Facilities Council‘s (STFC’s) Rutherford Appleton Laboratory and UK Astronomy Technology Centre and the Cavendish Laboratory at Cambridge University, the University of Manchester and the University of Kent all of whom played key roles in the design and construction of ALMA.

John Richer, UK Project Scientist for ALMA, based at Cambridge University said; ‘‘ALMA will be the only observatory capable of imaging the details of star and planet formation in our Galaxy, and the details of how dusty distant galaxies form and evolve in the early Universe. To make the scientific breakthroughs for which ALMA was designed, we will have to wait patiently for all 66 ALMA antennas to arrive. Nonetheless, the successful linking of the first three antennas demonstrates that all the major elements of the telescope are functioning, and that the basic design is sound. Astronomers can now look forward eagerly to the first scientific images from ALMA, which should arrive in less than two years from now”.

The successful linking of the antenna trio was a key test of the full electronic and software system now being installed at ALMA, and its success anticipates the future capabilities of the observatory. When complete, ALMA will have at least 66 high-tech antennas operating together as an “interferometer”, working as a single, huge telescope, with an effective diameter exceeding 10 miles, probing the sky in the millimetre and submillimetre wavelengths of light. The combination of the signals received at the individual antennas is crucial to achieve images of astronomical sources of unprecedented quality at its designed observing wavelengths. The three-antenna linkup is a critical step towards the observatory’s operations as an interferometer. Although the first, successful measurements employing just two antennas were obtained at the ALMA high site from October 2009 (see European Southern Observatory (ESO) Announcement (link opens in a new window)) and demonstrated the excellent performance of the instruments, the addition of the third antenna is a leap of vital importance into the future of the observatory. This major milestone for the project is known as “phase closure” and provides an important independent check on the quality of the interferometry.

To achieve this crucial goal, astronomers observed the light coming from a distantextragalactic source, the quasar QSO B1921-293, well known to astronomers for its bright emission at very long wavelengths, including the millimetre/submillimetre range probed by ALMA. The stability of the signal measured from this object shows that the antennas are working impressively well.

Professor Richard Holdaway, Director STFC’s Space Science and Technology Department said; ‘‘To see the linking up of the third antenna at the site in Chile shows how a project which has been worked on in all corners of the globe can come together as seamlessly as if it had been created in the same institution. It is testament to all those involved that this project has gone so smoothly and I look forward to seeing the first results“.

Several additional antennas will be installed on the Chajnantor plateau over the next year and beyond, allowing astronomers to start producing early scientific results with the ALMA system around 2011. After this, the interferometer will steadily grow to reach its full scientific potential, with at least 66 antennas.

Leonardo Testi, the European Project Scientist for ALMA at ESO said; “The first signal using just two ALMA antennas, observed in October, can be compared to a baby’s first babblings. Observing with a third antenna represents the moment when the baby says its very first, meaningful word — not yet a full sentence, but overwhelmingly exciting! The linking of three antennas is indeed the first actual step towards our goal of achieving precise and sharp images at submillimetre wavelengths.”

ALMA, an international astronomy facility, is a partnership of Europe, North America and East Asia in cooperation with the Republic of Chile.

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Notes for editors

The Atacama Large Millimeter/submillimeter Array (ALMA), an international astronomy facility, is a partnership of Europe, North America and East Asia in cooperation with the Republic of Chile. ESO is the European partner in ALMA. ALMA, the largest astronomical project in existence, is a revolutionary telescope, comprising an array of 66 giant 12-metre and 7-metre diameter antennas observing at millimetre and submillimetre wavelengths. ALMA will start scientific observations in 2011.

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Contacts

• Lucy Stone
  Press Officer
  Rutherford Appleton Laboratory
  Tel: +44 (0)1235 445627
  Mobile: +44 (0) 7920 870125
  
  
• Dr John Richer
  UK Project Scientist for ALMA
  Cavendish Laboratory, Cambridge
  Tel: +44 (0)1223 337246

For further information from ESO please contact

• Wolfgang Wild
  ESO, Garching, Germany
  Tel: +49 89 3200 6716 (after 6 January)
  Mobile: +49 160 9411 7833
  
  
• Leonardo Testi
  ESO, Garching, Germany
  Tel: +49 89 3200 6541 (from 8 January 2010)
  
  
• Lars Lindberg Christensen
  ESO, Garching, Germany
  Tel: +49 173 38 72 621 (UT-5h)
  
  
• Richard Hook
  ESO, Garching, Germany
  Tel: +49 89 3200 6655
  
  
• Douglas Pierce-Price
  ESO, Garching, Germany

European Southern Observatory

ESO, the European Southern Observatory, is the foremost intergovernmental astronomy organisation in Europe and the world’s most productive astronomical observatory. It is supported by 14 countries: Austria, Belgium, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Portugal, Spain, Sweden, Switzerland and the United Kingdom. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world-class observing sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope, the world’s most advanced visible-light astronomical observatory, and VISTA (Visible and Infrared Survey Telescope for Astronomy), the world’s largest survey telescope. ESO is currently planning a 42-metre European Extremely Large optical/near-infrared Telescope, the E-ELT, which will become “the world’s biggest eye on the sky”.

Links

• More info: ESO ALMA web pages (link opens in a new window)
• More info: ALMA Observatory web pages (link opens in a new window)

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